My Gamertag is linked to an EA account that I no longer am able to manage and I'm unable to...

My current gamertag is linked to an EA account I created from my Xbox 360 13 years ago to play one of the early Battlefront games. My personal info and email address have since changed and I no longer have access to the email to confirm ownership. I now have a new EA account that I can manage but can't link it to my gamertag because of the old one. And EA and their "customer support" are unwilling (not unable, but unwilling) to assist. I can verify my Xbox account and current EA account but am unable to verify the old one so they refuse to delete or unlink it. Solutions?

:)